This too was a concern of mine...
You may already know that normal lube decreases sperm motility so they'll never make it to your egg... saliva is just as bad because you naturally have enzymes in your saliva made to break down food... same goes with the sperm, it will actually start to break down the little guys & weaken them or in some cases, deform them. I don't know if that will effect the unborn child or not, but it certainly decreases your chances of TTC. The best stuff I've found so far is PreSeed which I bought online. It mimics your own CM and helps the little guys with their motility to get to your egg. PreSeed seems to understand us women, I also got 2 free HPTs with my order! I guess they know how crazy we can all get with the HPTs and how much they cost! Lots of luck to you all, I'm thinking of you and sending baby dust through this keyboard!
I heard it call kill some, but really, I don't think that much is still present when you actually BD (if you were "playing around" beforehand). I think if it's gobs of it, then I would worry.